A line segment that passes through the center of a circle is known as a diameter. The diameter connects two points on the circle and goes through its center, cutting the circle into two equal halves.
The length of the diameter is always twice the length of the radius, which is the distance from the center of the circle to any point on its circumference. Understanding the concept of a diameter is fundamental in geometry, as it helps with calculating various properties of circles, including area and circumference.